WO2003067182A1

WO2003067182A1 - Shearing interference measuring method and shearing interferometer, production method of projection optical system, projection optical system, and projection exposure system

Info

Publication number: WO2003067182A1
Application number: PCT/JP2003/000897
Authority: WO
Inventors: Zhigiang Liu
Original assignee: Nikon Corporation
Priority date: 2002-02-07
Filing date: 2003-01-30
Publication date: 2003-08-14
Also published as: AU2003244344A1; JP2003302205A

Abstract

A shearing interference measuring method capable of measuring without being affected by disturbance and aberration on a light source side. The shearing interference measuring method comprises the steps of dividing a measuring light flux output from a light source to produce two light fluxes having their wave fronts deviated from each other, projecting those two light fluxes with their wave fronts deviated onto an inspection subject, and detecting interference fringe occurring at a position at which the wave fronts of the two light fluxes passed through the inspection subject overlap each other.

Description

Specification

TECHNICAL FIELD The present invention relates to a shearing interference measuring method and a shearing interferometer, a method of manufacturing a projection optical system, a projection optical system, and a method of manufacturing a projection optical system. , And a projection exposure apparatus.

It has been proposed to apply a shearing interferometer to the inspection of high-precision optical systems such as projection lenses.

FIG. 14 is a diagram showing a conventional shearing interferometer. Fig. 14 (a) shows a shearing interferometer that measures the transmitted wavefront of the test object (here, the projection optical system PL), and Fig. 14 (b) shows the wavefront of the return light from the test object (here, the PL). And a shearing interferometer for measuring the reflected wavefront of the test surface 4).

In the shearing interferometer shown in FIG. 14 (a), a measurement light beam L (a spherical wave diverging from one point of a reticle surface R, which is an object surface) is made incident on an optical system PL to be inspected, and the optical system PL is subjected to measurement. The measurement light beam L emitted from the light analysis system PL is split into two light beams L 1 and L 2 whose wavefronts are shifted from each other by the diffractive optical element 2, and the interference fringes due to the light beams L 1 and L 2 are captured by the CCD camera 3. Observed by such as. From this interference fringe, the shape of the transmitted wavefront of the test optical system PL is determined.

On the other hand, in the shearing interferometer shown in FIG. 14B, the measurement light beam L (a light beam that is incident substantially perpendicularly to the test surface 4) is incident on the test surface 4, and the measurement light beam L is incident on the test surface 4. The reflected measurement light beam L is split by a half mirror HM2 etc. into two light beams L l and L 2 (not shown) whose wavefronts are shifted from each other, and the interference fringes caused by these light beams LI and L 2 are observed by a CCD camera 3 etc. Is what you do. From this interference fringe, the shape of the reflected wavefront of the test surface 4 is determined.

However, when compared with other interferometers such as the Fizeau type, the measurement accuracy of these conventional shearing interferometers greatly affects disturbances and aberrations on the light source side of the interferometer. There is a fundamental problem that

Because, in other interferometric measurements, the two light beams branched from the same light source interfere without shifting the wavefront, so the wavefront (hereinafter referred to as the “noise wavefront”) that indicates the disturbance and aberration on the light source side superimposed on the wavefronts of the two light beams, respectively The interference fringes generated by the overlap between the two light beams and the phase difference distribution between the wavefronts of the two light beams are not affected by the noise wavefront. On the other hand, in a shearing interferometer, two light beams (light beams L 1 and L 2 in Fig. 14) branched from the same light source interfere with each other by shifting their wavefronts. And affect the interference fringes. Disclosure of 昍

An object of the present invention is to provide a shearing interferometer and a shearing interferometer capable of performing measurement without being affected by disturbance or aberration on the light source side.

Another object of the present invention is to provide a method of manufacturing a high-performance projection optical system by applying the shearing interference measurement method.

Another object of the present invention is to provide a high-performance projection optical system.

Another object of the present invention is to provide a high-performance projection exposure apparatus.

For this reason, in the shearing interference measurement method of the present invention, the measurement light beam emitted from the light source is divided to generate two light beams having wavefronts shifted from each other, and the two light beams are applied to the test object with the wavefronts shifted. Light is projected, and interference fringes occurring at positions where the wavefronts of the two light beams passing through the test object overlap are detected.

The interference fringes formed by the two light beams at that position are affected by the transmitted wavefront (signal wavefront) corresponding to the aberration of the test object, but are not affected by disturbance or aberration on the light source side. Therefore, according to this shearing interference measurement method, measurement can be performed without being affected by disturbance or aberration on the light source side.

Preferably, in this shearing measurement method, a phase shift interferometry for detecting the interference fringes a plurality of times while shifting the phase of the two light beams is applied. By doing so, measurement accuracy can be improved.

Further, the shearing interferometer of the present invention is arranged in the optical path of the measurement light beam emitted from the light source, and divides the measurement light beam to generate two light beams having different wavefronts. A split optical system for projecting the two light beams onto the object with their wavefronts shifted, and a detector disposed at a position where the wavefronts of the two light beams transmitted through the object overlap each other. . According to this shearing interferometer, it is possible to perform measurement without being affected by disturbance or aberration on the light source side.

Preferably, in this shearing interferometer, the arrangement position of the detector is a position conjugate with the division plane of the division optical system. With this configuration, it is possible to reliably perform the measurement that is not affected by the disturbance variance on the light source side.

Also preferably, in this shearing interferometer, the optical path of the two light beams that passes through the test object and enters the detector is divided into two light beams, and the wavefronts of the two light beams are placed on the detector. Are arranged.

Preferably, in the shearing interferometer, the splitting optical system for splitting the measurement light beam and the splitting optical system for splitting the two light beams have a conjugate relationship. Preferably, in this shearing interferometer, a mask for cutting light other than the two light beams whose wavefronts overlap on the detector is arranged in the optical path of the two light beams. In this way, measurement accuracy can be improved.

Also, preferably, in this shearing interferometer, the split optical system comprises a diffractive optical element.

Further, the shearing interferometer of the present invention is arranged in the optical path of the measurement light beam emitted from the light source, and divides the measurement light beam to generate two light beams whose wavefronts are deviated from each other, and combines the two light beams. A split optical system for projecting light to the test object with a wavefront shifted, and a detector arranged at a position where the wavefronts of the two light beams returning from the test object to the split optical system overlap each other. It is characterized by. According to this shearing interferometer, it is possible to perform measurement without being affected by disturbance or aberration on the light source side.

Preferably, in the shearing interferometer, the splitting optical system includes: a beam splitter that splits the measurement light beam into two light beams of a transmitted light beam and a reflected light beam; and the two light beams split by the beam splitter. A deflecting optical system for projecting light on the test object with the wavefronts shifted from each other.

Preferably, in the shearing interferometer, a polarization beam splitter is used in the beam splitter, and a polarization beam splitter is used between the split optical system and the detector. A polarizing plate is arranged in the optical path of the two light beams. In this way, measurement accuracy can be improved.

Preferably, in the shearing interferometer, the position of the detector is a position conjugate with the surface of the test object. With this configuration, it is possible to reliably perform the measurement that is not affected by the disturbance variance on the light source side.

Preferably, in this shearing interferometer, a mask for cutting light other than the two light beams whose wavefronts overlap on the detector is arranged in the optical path of the two light beams. In this way, measurement accuracy can be improved.

Further, a method of manufacturing a projection optical system according to the present invention includes a procedure for inspecting a part or all of the projection optical system by the shearing interference measurement method of the present invention. Since the shearing interference measurement method of the present invention can perform high-accuracy measurement, the inspection is performed with high accuracy. Therefore, according to the method for manufacturing a projection optical system of the present invention, a high-performance projection optical system can be manufactured.

Further, a projection optical system according to the present invention is manufactured by the method for manufacturing a projection optical system according to the present invention. Such a projection optical system has high performance.

Further, a projection exposure apparatus of the present invention includes the projection optical system of the present invention. Such a projection exposure apparatus has high performance.

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FIG. 1A is a configuration diagram of the shearing interferometer of the first embodiment, and FIG. 1B is a diagram illustrating an alignment method of the shearing interferometer of the first embodiment.

FIG. 2 is a diagram showing a modified example of the shearing interferometer of the first embodiment.

FIG. 3A is a configuration diagram of the shearing interferometer of the second embodiment, and FIG. 3B is a diagram illustrating an alignment method of the shearing interferometer of the second embodiment.

FIG. 4 is a diagram illustrating the shearing interferometer of the second embodiment in which the imaging surface of the CCD camera 3 and the diffractive optical element G21 are in a conjugate relationship.

FIG. 5 is a diagram showing a modified example of the shearing interferometer of the second embodiment.

FIG. 6A is a configuration diagram of the shearing interferometer of the third embodiment. FIG. 6 (b) is a diagram showing the optical paths 1 ^ 1, R2 of the light beams L1, 2 of this shearing interferometer. FIG. 7 is a diagram illustrating an application example of the shearing interferometer of the third embodiment.

FIG. 8 is a diagram showing a modified example of the shearing interferometer of the third embodiment.

FIG. 9A is a configuration diagram of the shearing interferometer of the fourth embodiment. FIG. 9B is a diagram showing the optical paths 11 and R2 of the light beams L1 and L2 of the shearing interferometer. FIG. 10 is a diagram illustrating a modified example of the shearing interferometer of the fourth embodiment.

FIG. 1.1 is a configuration diagram of the shearing interferometer of the fifth embodiment.

FIG. 12 is a configuration diagram of the shearing interferometer of the sixth embodiment.

FIG. 13 is a schematic configuration diagram of the projection exposure apparatus of the seventh embodiment.

FIG. 14 is a diagram showing a conventional shearing interferometer. Sun》荬

Hereinafter, embodiments of the present invention will be described with reference to the drawings. .

[First Embodiment]

A first embodiment of the present invention will be described with reference to FIG.

In the present embodiment, a shearing interferometer of the present invention of a type for measuring a transmitted wavefront of a test object and a shearing interferometer thereof will be described.

FIG. 1A is a configuration diagram of the shearing interferometer of the present embodiment.

Here, the description will be made on the assumption that the test object is the projection optical system P L (for example, EUVL) of the projection exposure apparatus, but the present invention can be applied to other test objects.

In the shearing interferometer, a measurement light beam (hereinafter, referred to as a spherical wave diverging from one point of the reticle surface R) enters the projection optical system PL from the reticle surface R side. In addition, a detector such as a CCD camera 3 is arranged on the wafer surface W side of the projection optical system PL.

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The measurement light beam L is generated by collecting a light beam emitted from a light source (not shown) on the reticle surface R.

Here, in the shearing interferometer of the present embodiment, a split optical element (for example, a diffractive optical element G11) is included in the measurement light beam L on the reticle surface R side. ) Is inserted.

Here, the insertion position of the diffractive optical element Gl1 is determined by the focusing position of the measurement light beam L (L The light source side is closer to the tickle surface R).

The diffractive optical element Gl1 divides the measurement light beam L to generate two light beams L1 and L2 whose wavefronts are shifted from each other. For example, the 0th-order diffracted light and the 1st-order diffracted light generated in the diffractive optical element G11 are used as the light flux L1 and the light flux L2, respectively. In FIG. 1 (a), the wavefront of the light beam L1 and the wavefront of the light beam L2 are shifted in the horizontal direction (object height direction), and the light-collecting positions of both light beams are shifted from each other on the reticle surface R. Was shown.

Here, in the diffractive optical element G11, extra light other than the light fluxes L1 and L2 is also generated.

Therefore, in the present embodiment, it is preferable to dispose a mask Ml1 for cutting the extra light on the exit side of the diffractive optical element G11.

By the way, the most efficient cut can be made when it is placed near the focal point (here, near the reticle surface R).

As shown in the lower part of FIG. 1 (a), this mask M11 has openings at the light-condensing point of the light beam L1 and the light-condensing point of the light beam L2, respectively, and the other parts are light-shielded. It is a mask that became a department.

The light beam L1 and the light beam L2 that have passed through the mask M11 and then have passed through the projection optical system PL are condensed on the wafer surface W (at positions shifted from each other).

Further, as shown in FIG. 1A, the imaging surface of the CCD camera 3 of the present embodiment is arranged at a position conjugate with (the diffraction surface of) the diffraction optical element G11 with respect to the projection optical system PL. In the shearing interference measurement of the present embodiment, based on the output of the CCD camera 3, the shear direction and the shear amount from the measurement light beam L to the light beams Ll and L.2, it corresponds to the aberration of the projection optical system PL. Calculate the transmitted wavefront.

The shear amount and shear direction can be obtained from the design data of the shearing interferometer and the data measured by the shearing interferometer.

Now, in the above-described shearing interferometer, a noise wavefront due to disturbance or aberration on the light source side is superimposed on the wavefront of the measurement light beam L.

Therefore, the same noise wavefront is superimposed on the wavefront of the light beam L1 and the wavefront of the light beam L2 obtained by dividing the measurement light beam L. However, in this shearing interferometer, at the position conjugate to the diffractive optical element G11 with respect to the projection optical system PL (here, the imaging surface of the CCD camera 3), the noise wavefront superimposed on the wavefront of the light flux 1 The noise wavefront superimposed on the wavefront of the light beam L2 just overlaps, and the phase difference between the noise wavefronts is almost zero.

On the other hand, since the light beam L1 and the light beam L2 enter the projection optical system PL with their wavefronts shifted from each other, the transmission corresponding to the aberration information of the projection optical system PL superimposed on the light beam L1 The wavefront (signal wavefront) and the signal wavefront superimposed on the light beam L2 are shifted from each other at the position, and a phase difference distribution is generated.

As a result, the interference fringes formed by the light beam L1 and the light beam L2 on the imaging surface of the CCD camera 3 arranged at that position are affected by the transmitted wavefront (signal wavefront) corresponding to the aberration of the projection optical system PL. On the other hand, it is not affected by the noise wavefront.

Therefore, based on the output of the CCD camera 3, measurement that is not affected by disturbance or aberration on the light source side can be performed.

Next, in the present embodiment, an alignment method for ensuring a cooperative relationship between the diffractive optical element G11 and the CCD camera 3 will be described.

FIG. 1B is a diagram illustrating an alignment method of the shearing interferometer of the present embodiment.

In this alignment, it is detected whether or not the conjugate relationship is set based on whether or not the light flux L1 and the light flux L2 are substantially overlapped on the imaging surface of the CCD camera 3. At the time of alignment, first, a target T that partially blocks the measurement light L is placed in the measurement light L incident on the diffractive optical element Gl1, and one of the light L1 and the light L2 is shielded. One of the openings of the mask M11 is shielded from light.

It is preferable that the target T is disposed at a position as close as possible to the diffractive optical element G11.

In order to shield one of the light beam L1 and the light beam L2, the opening of the mask M11 is arranged only at one of the light-condensing points of the light beam L1 and the light beam L2, and the other light-condensing portion The mask M11 may be shifted in the reticle plane R so that the light shielding portion of the mask M11 is arranged at a point.

In this state, one of the light flux L 1 and the light flux L 2 is provided on the imaging surface of the CCD camera 3. Only in the evening, an image of the gate T is formed.

From the output of the CCD camera 3 at this time, the formation of the image of the evening gate T on the imaging surface is directly remembered.

Further, with the target T arranged at the same position, the output of the CCD camera 3 is referred to while the other of the light beam L.l and the light beam L2 is shielded, and the position of the formation of the target T on the imaging surface is determined. The positions of the diffractive optical element Gl1 and the CCD camera 3 are adjusted so as to be the same as the stored formation positions.

In this way, the alignment can be made easily.

(Modification of the first embodiment)

In the above description, the position at which the diffractive optical element Gl1 is disposed is on the light source side with respect to the reticle surface R (see FIG. 1). However, in this modified example, as shown in FIG. Is positioned closer to the projection optical system PL than the reticle surface. A diffractive optical element according to the present modification is indicated by reference numeral G 11 'in FIG.

The mask M 11 ′ for cutting off the extra light generated in the diffractive optical element G 11 may be arranged near the wafer surface W as shown in FIG. In this case as well, the CCD camera 3 is arranged at a position conjugate with (the diffraction surface of) the diffractive optical element G 11 ′ with respect to the projection optical system PL.

[Second embodiment]

A second embodiment of the present invention will be described based on FIG.

In the present embodiment as well, as in the first embodiment, an evening shearing interferometer of the present invention for measuring a transmitted wavefront of a test object and a shearing interference method thereof will be described. Here, only the differences from the first embodiment will be described, and the description of the other parts will be omitted.

FIG. 3A is a configuration diagram of the shearing interferometer of the present embodiment.

The difference in configuration from the shearing interferometer of the first embodiment shown in FIG. 1 is that the diffractive optical element as a split optical element is not only on the reticle surface R side of the projection optical system PL but also on the wafer surface W side. It is also located at the point.

This is also the case with the configuration of the conventional shearing interferometer shown in FIG. 14 (a). 7

In this configuration, a diffractive optical element as a nine-segment optical element is additionally arranged on the reticle surface R side of the projection optical system PL.

That is, in the shearing interferometer of the present embodiment, diffractive optical elements G 21 and G 22 are arranged on the reticle surface R side and the wafer surface W side, respectively.

The diffractive optical element G21, like the diffractive optical element G11 of the first embodiment, generates two light beams L1 and L2 whose wavefronts are shifted from each other.

For example, the 0th-order diffracted light and the 1st-order diffracted light generated in the diffractive optical element G21 are used as the light flux Ll and the light flux L2, respectively.

On the other hand, the diffractive optical element G22 integrates the two light beams L1 and L2 emitted from the projection optical system PL with a displacement equivalent to that of the diffractive optical element G21 to form one light beam (reverse To do).

Such a diffractive optical element G22 is designed in advance according to the diffraction pattern of the diffractive optical element G11, the magnification of the projection optical system PL, the wavelength used, and the like.

In this shearing interferometer, due to the interaction of the diffractive optical element G 21, the projection optical system PL, and the diffractive optical element G 22, the noise wave front superimposed on the wave front of the light flux L 1 and the light flux L 2 The noise wavefront superimposed on the wavefronts just overlaps, and the phase difference between the noise wavefronts is almost zero.

Therefore, the interference fringes formed by the light beam L1 and the light beam L2 at that position are affected by the transmitted wavefront (signal wavefront) corresponding to the aberration of the projection optical system PL, but are not affected by the noise wavefront.

Furthermore, in the shearing interferometer of the present embodiment, the diffractive optical element G 22 (the diffractive surface thereof) is arranged at a position conjugate with the diffractive optical element G 21 (the diffractive surface thereof) with respect to the projection optical system PL. Since the focal point of the light beam L1 and the focal point of the light beam L2 coincide on the wafer surface W, the wavefront of the light beam L1 and the wavefront of the light beam L2 can travel in the same direction. The interference fringes can be made almost one color.

In general, the closer to one color (ie, the larger the fringe interval of the interference fringes), the higher the fringe detection accuracy of the CCD camera 3 and the higher the measurement accuracy. At this time, since the wavefront of the light beam L1 and the wavefront of the light beam L2 after exiting from the diffractive optical element G22 always travel while overlapping, the position in the optical axis direction of the CCD camera 3 is changed. The degree of freedom is given to the position.

Therefore, the imaging surface of the CCD camera 3 can be arranged, for example, at a position conjugate with the pupil of the projection optical system PL, and the evaluation of the projection optical system PL based on the observed interference fringes can be facilitated.

In the present embodiment, it is preferable to use a mask in order to cut off excess light.

In this embodiment, since two diffractive optical elements are used, it is preferable that two masks are also used.

That is, as shown in FIG. 3A, the extra light generated by the diffractive optical element G 21 is cut by the mask M 21 arranged on the reticle surface R, and the diffractive optical element G 2 The extra light generated in 2 is cut by the mask M22 arranged on the wafer surface W surface.

Note that the light beam L1 and the light beam L2 emitted from the diffractive optical element G22 are condensed at the same point, so that the mask M22 may have only one opening.

Next, in this embodiment, an alignment method for ensuring the above-described conjugate relationship between the diffractive optical element G21 and the diffractive optical element G22 will be described.

FIG. 3B is a diagram for explaining an alignment method of the shearing interferometer of the present embodiment.

This alignment method is the same as the alignment method of the shearing interferometer of the first embodiment, except that the position adjustment target is the diffractive optical element G21 and the diffractive optical element G22.

That is, also in the alignment of the present embodiment, first, in the measurement light beam L incident on the diffractive optical element G 21, a sunset T which partially blocks the measurement light beam L is arranged, and at the same time, the light beams L 1 and L 2 One of the openings of the mask M21 is shielded so as to shield one of the openings.

It is preferable that the target T is disposed at a position as close as possible to the diffractive optical element G21.

Further, in order to shield one of the light beam L1 and the light beam L2, the opening of the mask M21 is arranged only at one of the light-condensing points of the light beam L1 and the light beam L2, and the other light-condensing point To The mask M21 may be shifted in the reticle plane R plane so that the light shielding portion of the mask M21 is arranged.

In this state, an image of the evening gate T by only one of the light flux Ll and the light flux L2 is formed on the imaging surface of the CCD camera 3.

Therefore, the position where the image of the target T is formed on the imaging surface is stored from the output of the CCD camera 3 at this time.

Furthermore, while the target T is arranged at the same position and the other of the light beam L1 and the light beam L2 is shielded, the output of the CCD camera 3 is referred to, and the formation position of the sunset T on the imaging surface is determined. The positions of the diffractive optical element G21 and the diffractive optical element G22 are adjusted so that is the same as the stored formation position.

FIG. 4 shows that the diffractive optical element G21 and the diffractive optical element G22 are non-conjugated in the shearing interferometer of the present embodiment, and instead, the imaging surface of the CCD camera 3 and the diffractive optical element G21 FIG. 4 is a diagram showing a case where a diffraction surface (a diffraction surface) is set to a conjugate relationship.

Even if the diffractive optical element G21 and the diffractive optical element G22 are not set to a conjugate relationship, if the imaging surface of the CCD camera 3 and the (diffractive surface of) the diffractive optical element G21 are set to a conjugate relation, The noise wavefront superimposed on the wavefront of the light beam L1 and the noise wavefront superimposed on the wavefront of the light beam L2 overlap on the imaging surface of the CCD camera 3.

Therefore, the same effect as in the first embodiment can be obtained.

In this case, the alignment may be performed by setting the position adjustment target to the diffractive optical element G21 or the CCD camera 3 in the above-described alignment method (see FIG. 3B). (Modification of Second Embodiment)

Here, only the differences from the shearing interferometer of the second embodiment will be described, and the description of the other parts will be omitted. Further, similarly to the modified examples described below, the shearing interferometer of the first embodiment can be modified.

In the above-described second embodiment, the direction of deviation between the wavefront of the light beam 1 and the wavefront of the light beam L2 is referred to as the “lateral direction” (object height direction). As described above, the term “wavefront direction” (direction along the wavefront) is used. Therefore, a diffractive optical element G 21, and a diffractive optical element G 22 ′ are provided between the diffractive optical element G 21 and the reticle surface R and between the diffractive optical element G 22 and the wafer surface W, respectively. Inserted.

The diffractive optical element G 21 ′ is designed in advance so that the focal points of the light beam L 1 and the light beam L 2 emitted from the diffractive optical element G 21 coincide.

The diffractive optical element G22 'is designed in advance so that the converging points of the light beam L1 and the light beam L2 emitted from the diffractive optical element G22 coincide.

Since the light-gathering points coincide with each other, only one opening of the mask 31 is arranged on the reticle surface R in the sealing interferometer of the present embodiment, as shown in FIG.

[Supplement to the first embodiment and the second embodiment]

In each of the above embodiments, if the interference fringes are detected while shifting at least one of the diffractive optical elements in the same direction as the wavefront dividing direction (that is, if the phase shift interferometry is applied, ) The measurement accuracy can be further improved.

Also, in the inspection of a test object using a special wavelength (short wavelength) such as EUVL, it is difficult to use a refraction member as an optical element of a shearing interferometer (because a refraction member that transmits a special wavelength). However, in each of the above embodiments, a diffractive optical element was used as the split optical element. However, a lens may be used for a part or all of the split optical element for a test object that can use a refraction member.

Further, in each of the above embodiments, the direction of division of the light fluxes L 1 and L 2 is “horizontal direction” or “wavefront direction”, but may be the optical axis direction (vertical direction).

[Third embodiment]

A third embodiment of the present invention will be described based on FIGS. 6, 7, and 8. FIG.

In the present embodiment, a shearing interferometer of the present invention of a type for measuring the wavefront of reflected light from the test object (reflected wavefront of the test surface 4) and a shearing interference method thereof will be described. FIG. 6A is a configuration diagram of the shearing interferometer of the present embodiment. FIG. 6B is a diagram showing the optical paths R 1 and R 2 of the light beams L 1 and L 2 of the shearing interferometer.

The shearing interferometer has a light source 5 such as a laser that emits a measurement light beam L to be incident on the surface 4 to be measured, and the measurement light beam L is divided before being incident on the surface 4 to be measured. The split optical system 34 generates two shifted light beams L 1 and L 2 and projects them on the test surface 4 with the wavefront shifted, and returns to the split optical system 34 after being reflected by the test surface 4. A CCD camera 3 for detecting interference fringes caused by the light beams L 1 and L 2 is provided. Reference numeral 6 denotes a beam spreader that converts the measurement light beam L emitted from the light source 5 into a parallel light beam.

Reference numeral HM33 denotes a half mirror for guiding the light beams L 1 and L 2 reciprocating in the split optical system 3 in the direction of the CCD force camera 3.

Reference numeral 7 denotes an imaging optical system that forms an image of a light beam (light beam 1, L 2) incident on the CCD camera 3.

Here, the test surface 4 and the imaging surface of the CCD camera 3 are in a conjugate relationship via the split optical system 34, the half mirror HM33, and the imaging optical system 7.

Note that, in other embodiments described later, the test surface 4 and the imaging surface of the CCD camera 3 have a conjugate relationship via an optical system disposed therebetween.

First, the split optical system 34 is composed of two beam splitters P 34-1 and P 34-2, and mirrors M 34-1 and 34-2.

The measurement light beam L is split into a transmitted light beam and a reflected light beam (hereinafter, the transmitted light beam is referred to as a light beam L1 and the reflected light beam is referred to as a light beam L2) at a beam splitter P34-2.

The light beam L1 is reflected by the mirror M34-1 and is incident on the beam splitter P34-1, and the light beam L2 is reflected by the mirror M34-2 and is incident on the beam splitter P34-11.

The beam splitter P34-1 transmits the light flux L1 and emits the light to the surface 4 to be measured, and also reflects the light flux L2 and emits the light to the surface 4 to be measured.

Further, the position of the mirror M 34-2 beam splitter P 34-1 is measured in a state where the light beams L 1 and L 2 are shifted from each other (in a state where the optical axis is shifted). Adjusted to be incident on surface 4.

Further, the light beams L 1 and L 2 emitted from the splitting optical system 34 to the surface 4 to be detected and reflected on the surface 4 to be tested are transmitted through the splitting optical system 34 in the opposite direction, and then are transferred to the half mirror H M33 by the CCD. It is deflected in the direction of camera 3 and forms interference fringes on the imaging surface of CCD camera 3. In the shearing interference measurement according to the present embodiment, based on the output of the CCD camera 3 and the shear direction and the shear amount from the measurement light beam L to the light beams Ll and L2, it corresponds to the unevenness of the surface 4 to be measured. Calculate the reflected wavefront.

The shear amount and shear direction can be obtained from the design data of the shearing interferometer and the data actually measured by the shearing interferometer.

Here, also in the shearing interferometer having the above configuration, a noise wavefront due to disturbance or aberration on the light source side (beam expander 6, light source 5) is superimposed on the wavefront of the measurement light beam L.

Therefore, the same noise wavefront is superimposed on the wavefront of the light beam L1 and the wavefront of the light beam L2 obtained by dividing the measurement light beam L.

However, the light beam L1 passing through the optical path R1 and the light beam L2 passing through the optical path R2 shown in FIG. 6 (b) reciprocate in a specific optical path in the split optical system. Therefore, the light beam L1 and the light beam L2 absorb the mutual wavefront shift (shift of the optical axis), and overlap each other after reciprocation (the optical path R1 is a half mirror HM33). → Beam split P 34—2 → Mirr M 34-1 → Beam split ヅ P 34—1 Test surface 4 Beam split ヅ Ear P 34— l → Mirr M34 The light path R2 is the half mirror HM33 → beam splitter P34—2 → mirror M34—2 → beam splitter P34—1 The surface to be measured 4 beams. Splitter P34—1 → Mirror M 34—2 Beamspring 夕 Evening P 34—2 This is the optical path of Half Mirror HM33.

Therefore, on the imaging surface of the CCD camera 3, the noise wavefront superimposed on the wavefront of the light beam L1 and the noise wavefront superimposed on the wavefront of the light beam L2 overlap, causing interference fringes. I won't let you.

On the other hand, the luminous flux L 1 passing through the optical path R 1 and the luminous flux L 2 passing through the optical path R 2 are shifted from each other when they are incident on the surface 4 to be measured. Therefore, the reflected wavefront (signal wavefront) corresponding to the unevenness of the surface 4 to be measured, which is superimposed on the wavefront of the light beam L1, and the signal wavefront superimposed on the wavefront of the light beam L2, are the wavefront of the light beam L1. When the wavefront of the light beam L2 overlaps with the wavefront of the light beam L2, they deviate from each other.

Therefore, on the imaging surface of the CCD camera 3, the light is superimposed on the wavefront of the light beam L1, The reflected wavefront (signal wavefront) corresponding to the unevenness of the test surface 4 and the signal wavefront superimposed on the wavefront of the light beam L2 do not overlap, and generate interference fringes.

As a result, the interference fringes formed by the light flux L1 and the light flux L2 on the imaging surface of the CCD camera 3 are affected by the reflected wavefront (signal wavefront) corresponding to the unevenness of the surface 4 to be measured, while the noise wavefront is Not affected by

Therefore, based on the output of the CCD camera 3, it is possible to perform measurement without being affected by disturbance or aberration on the light source side.

In this embodiment, the beam splitter P 34 is used to increase the light amount of the light beam L 1 passing through the optical path R 1 and the light beam L 2 passing through the optical path R 2 to enhance the detection accuracy of interference fringes. -Polarizing beam splitter is used as 1 or beam splitter P 34-2, and polarizing plate 35 is provided in front of CCD camera 3 (for example, between imaging optical system 7 and half mirror HM 33). Inserted.

For example, if a polarizing beam splitter is used as the beam splitter P34_1, the P-polarized light of the light beam L1 transmitted through the beam splitter P34-2 is reflected on the surface 4 to be measured. Later, the light returns to the direction of the optical path R 1, and the S-polarized light of the light beam L 2 reflected by the beam splitter P 3 4 12 returns to the direction of the optical path R 2 after the reflection on the surface 4 to be measured.

In order to further improve the detection accuracy, it is preferable that a polarization beam splitter is used for both the beam splitter P34-1 and the beam splitter P34-2.

By doing so, the P-polarized light component of the measurement light beam L is surely set to the light beam L1 passing through the optical path R1, and the S-polarized light component of the measurement light beam L is surely changed to Since the light beam L2 can pass through the optical path R2, the loss of light amount can be suppressed.

If two polarizing beam splitters are used together, the deterioration of the extinction ratio of each polarizing beam splitter is compensated for by each other.

Further, if a known phase shift interferometry is applied to the above-described shearing interference measurement, the measurement accuracy is further improved.

To perform phase shift in this shearing interferometer shown in Fig. 6 (a), for example, For example, one or both of the mirror M34-1 and the mirror M34-2 may be slightly moved. '

The moving direction is the direction in which the difference between the optical path lengths R 1 and R 2 of the light beams L 1 and L 2 changes (for example, the direction indicated by the arrow in FIG. 6A).

In the phase shift interferometry, the output data of the CCD camera 3 (luminance distribution data of interference fringes) is sampled a plurality of times during this phase shift. The calculation method is, for example, as follows.

The luminance distribution I of the interference fringes occurring on the imaging surface is

I2 I 0 + Acos [T— T (s) + 261 + ∑ B icos (N i + d)

It is represented by

Where I 0 is the DC component of the luminance distribution of the interference fringes, A is the amplitude of the luminous flux LI, L 2, B i is the amplitude of various noises, and i is the number of each interference fringe due to various noises. N i is the phase distribution of the interference fringes due to each noise, 5 is the phase modulation by the phase shift of each interference fringe, and T is the shape of the reflected wavefront (signal wavefront) corresponding to the unevenness of the surface 4 to be measured. (Unit: phase), and T (s) is a change in wavefront shape (unit: phase) due to shearing of the measurement light beam L into the light beam L1 or the light beam L2. ∑ f (i) is the sum of each i of f.

For example, when eight luminance distribution data II, ... I8 are sampled while gradually shifting the phase by ΤΓ / 2 as a phase shift, each luminance distribution data II, ... Is represented as

1 1 = 10 + Acos [T-T (s) + ∑ B i cos (N i)

1 2 = 1 0 + Acos [T -T (s + 7Γ / 2) + ∑ B icos (N i + 7Γ / 4)

1 3 = 1 0 + Acos [T— T (s + 7Γ) + ∑ B icos (N i + 7Γ / 2)

1 4 = 10 + Acos [T-T (s + 3 ττ / 2) + ∑ B icos (N i + 3

1 5 = 1 0 + Acos [T-T (s + 27Γ) + ∑ B icos (N i + 7Γ)

1 6 = 1 0 + Acos [T— T (s + 7Γ / 2) + ∑ B icos (N i + 5 TT / 4)

1 7 = 1 0 + Acos [T-T (s + 7Γ) + ∑ B icos (N i + 3 TT / 2)

1 8 = 1 0 + Acos [T— T (s + 37Γ / 2) + Σ icos (Ν Ϊ + 77Γ / 4) 11 + 15 = 210 + 2 A cos [T— T (s)]

12 + 16 = 210 + 2 A cos [T-T (s) + ττ / 2]

13 + 17 = 210 + 2 A cos [T— T (s) + ττ]

14 + 18 = 2 1 0 + 2 ACQS [T— T (s) + 3 ττ / 2]

By adding / subtracting the luminance distribution data I 1, ··· I 8 as shown below, the effects of various noises can be canceled and the phase distribution of interference fringes due to the light fluxes L 1 and L 2 (T—T (s) ) Can be determined accurately.

Then, if the value of T (s) is obtained from the shearing interferometer, only the shape T of the reflected wavefront (signal wavefront) corresponding to the unevenness of the test surface 4 can be obtained.

(Application Example and Modification Example of Third Embodiment)

FIG. 7 is a diagram illustrating an application example of the shearing interferometer of the present embodiment. .

In the shearing interferometer shown in FIG. 6, the object to be measured is a flat surface 4 to be measured, but a curved surface 4 ′ is measured by using a wavefront conversion element 38 as shown in A in FIG. You can also. In addition, by using the folded reflecting surface 39 as shown in B in FIG. 7, not only the reflected wavefront of the test surface 4 but also the transmitted wavefront of the test object (such as the projection optical system PL) 4 ″ can be measured. .

FIG. 8 is a diagram illustrating a modified example of the shearing interferometer of the present embodiment.

In the case of using a half mirror as the beam splitter P 34-2 in the shearing interferometer shown in FIG. 6, it can be deformed as shown in FIG.

In the configuration shown in FIG. 8, the split optical system 34 uses a half-mirror HM 33 instead of one of the beam splitters P 34-2.

In this case, the measurement accuracy is lower than in the case of using the polarizing beam splitter, but the number of parts of the shearing interferometer can be reduced because the half mirror HM33 can be used as well.

[Fourth embodiment]

A fourth embodiment of the present invention will be described with reference to FIGS.

The present embodiment describes a shearing interferometer of the present invention of a type that measures the wavefront of the return light from the test object (the reflected wavefront of the test surface 4).

Here, only the differences from the shearing interferometer of the third embodiment will be described. The description of the other parts will be omitted.

FIG. 9A is a configuration diagram of the shearing interferometer of the present embodiment. FIG. 9 (b) is a diagram showing the optical paths 111 and R2 of the light beams L1 and L2 of this shearing interferometer. The splitting optics 44 of this shearing interferometer consists of a single beam splitter P44 and a single mirror M44. The reflection surface of the mirror M44 is arranged parallel to the reflection / transmission surface of the beam splitter P44.

The measurement light beam L is divided into a transmitted light beam and a reflected light beam (hereinafter, the transmitted light beam is referred to as a light beam L1 and the reflected light beam is referred to as L2) at a beam splitter P44.

The light beam L2 is projected onto the surface 4 to be measured as it is. The light beam L1 is reflected by the mirror M44, then re-enters the beam splitter P44, passes through the beam splitter P44, and is projected on the surface 4 to be measured.

The positions of the mirror M44 and the beam splitter P44 are adjusted so that the light beams L1 and L2 enter the surface 4 to be measured with their wavefronts shifted from each other (with the optical axis shifted). Have been.

Further, the light beams LI and L2 emitted from the splitting optical system 44 to the surface 4 to be measured and reflected on the surface 4 to be tested are transmitted to the half mirror 1 It is deflected in the direction of camera 3 and forms an interference fringe on the imaging surface of CCD camera 3.

Also in this shearing interferometer, the light beam L1 passing through the optical path R1 and the light beam L2 passing through the optical path R2 shown in FIG. 9 (b) reciprocate in a specific optical path in the splitting optical system 34. . Therefore, between the light beam L1 and the light beam L2, the mutual wavefront shift (shift of the optical axis) is absorbed, and the wavefront of the light beam L1 and the wavefront of the light beam L2 reciprocate. (Note that the optical path R 1 is the beam splitter P44 → mirror M44 → beam splitter P44 → test surface 4 beam splitter ヅ even P44 mirror M44 → beam splitter P44 → half mirror one The optical path of the HM33 is the optical path of the beam splitter P44 → the surface of the beam to be inspected 4 beam splitters, and the optical path of the half mirror HM33 is the optical path R2.

As a result, for the same reason as described in the third embodiment, the interference fringes formed by the light flux L1 and the light flux L2 on the image plane of the CCD camera 3 correspond to the unevenness of the surface 4 to be measured. While being affected by the reflected wavefront (signal wavefront), it is not affected by the noise wavefront due to disturbances and aberrations on the light source side (beam expander 6, light source 5).

Therefore, based on the output of the CCD camera 3, measurement can be performed without being affected by disturbance or aberration on the light source side.

In the present embodiment, the beam splitter P44 is used as the beam splitter P44 in order to increase the light amount of the light flux L1 passing through the light path R1 and the light flux L2 passing through the light path R2 to increase the detection accuracy of interference fringes. A polarizing beam splitter is used, and a polarizing plate 35 is inserted in front of the CCD camera 3 (for example, between the imaging optical system 7 and the half mirror HM 33). By doing so, the P-polarized light component of the measurement light beam L is surely set to the light beam L1 passing through the optical path R1, and the S-polarized light component of the measurement light beam L is surely changed to Since the light beam L2 can pass through the optical path R2, the loss of light amount can be suppressed.

Furthermore, if a known phase shift interferometry (for example, the method described in the third embodiment) is applied to the shearing interference measurement of the present embodiment, the measurement accuracy is further improved.

In order to perform a phase shift in the shearing interferometer shown in FIG. 9A, for example, one or both of the mirror M44 and the beam splitter P44 may be slightly moved.

The moving direction is a direction in which the difference between the optical path lengths 1 ^ 1 and R2 of the light fluxes L1 and L2 changes. (Modifications and application examples of the fourth embodiment)

When the beam splitter P44 is a polarization beam splitter, the shearing interferometer shown in FIG. 9 may be modified as shown in FIG. 10 and then the phase shift may be performed by another method. The phase shift method described below can be similarly applied to the third, fifth, and sixth embodiments.)

In the shearing interferometer shown in FIG. 10, a quarter-wave plate 45 is inserted on the incident side of the polarizing plate 35, and the polarizing plate 35 is rotatable around the optical axis. The main axis of the quarter-wave plate 45 is set to be 45 ° with respect to the P or S polarization direction of the light beams L 1 and L 2.

The light beam L 1 (linearly polarized light of P) and the light beam L 2 (of S (Linearly polarized light) is converted into circularly polarized light whose directions are opposite to each other.

At this time, if the polarizing plate 35 is rotated, the phase of the light beam L1 and the light beam L2 changes.

Therefore, according to the shearing interferometer, the phase shift can be performed by rotating the polarizing plate 35.

Further, when this phase shift is applied, it is not necessary to relatively move the mirror M 44 of the split optical system 44 and the beam splitter P 44.

Therefore, as shown by the dotted line in FIG. 10, a single split optical element 4 4 ′ having the mirror M 44 and the beam splitter P 44 fixed is used instead of the split optical system 44. You can also. .

Note that the shearing interferometer shown in FIG. 9 or FIG. 10 can also measure the curved test surface 4 ′ by using the wavefront conversion element 38 as shown in A in FIG.

In addition, if the reflection surface 39 is used as shown in FIG. 7B, not only the reflection wavefront of the test surface 4 but also the transmission wavefront of the test object (such as the projection optical system PL) 4 "is measured. You can do that too.

[Fifth Embodiment]

A fifth embodiment of the present invention will be described with reference to FIG.

The shearing interferometer according to the third embodiment and the shearing interferometer according to the fourth embodiment are of the type in which the shear direction is the horizontal direction. In the present embodiment, the case where the shear direction is the radial direction will be described.

Here, only the differences from the shearing interferometer shown in FIG. 8 will be described, and the description of the other parts will be omitted.

FIG. 11 is a configuration diagram of the shearing interferometer of the present embodiment.

The splitting optical system 54 of this shearing interferometer is composed of a beam splitter P34-1 and a beam splitter (here, a half mirror) HM33, a mirror M34-1, and a mirror M34-2. , And beam expanders R 54-1 and R 54-2 having different magnifications from each other.

The measurement light beam L is divided into a transmitted light beam and a reflected light beam (hereinafter, the transmitted light beam is referred to as a light beam Ll and the reflected light beam is referred to as a light beam L2) by a half mirror HM33. The light beam LI is reflected by the mirror M 34-1, and then enters the beam splitter P 34-1 via the beam expander R 54-1.

The light beam L 2 is reflected by the half mirror HM 33, then enters the mirror M 34-2 via the beam expander R 54-2, is reflected by the mirror M 34-2, and is reflected by the beam splitter 224. It is incident on P 3 4—1.

The beam splitter P 34-1 transmits the light beam L 1 and emits the light to the surface 4 to be measured, and also reflects the light beam L 2 and emits the light to the surface 4 to be measured.

In the split optical system 54, the light beam L1 and the light beam L2 incident on the surface 4 to be inspected have the same optical axis, but the beam expanders R54-1 and R54-2. Since the magnifications are different, the luminous flux diameter is shifted.

The light beam L 1 reciprocating in the beam expander R 54-1 and the light beam L 2 reciprocating in the beam expander R 54-2 absorb the mutual wavefront deviation (beam diameter deviation) due to the reciprocation. After the round trip. The wavefronts of each other overlap.

As a result, for the same reason as described in the third embodiment, the interference fringes formed by the light flux L1 and the light flux L2 on the image plane of the CCD camera 3 are reflected by the unevenness of the surface 4 to be measured. While being affected by the wavefront (signal wavefront), it is not affected by the noise wavefront due to disturbances and aberrations on the light source side (beam expander 6, light source 5).

[Sixth embodiment]

A sixth embodiment of the present invention will be described based on FIG.

The shearing interferometer according to the third embodiment and the shearing interferometer according to the fourth embodiment have a structure in which the shear is used to shift the optical axis, but a shearing interferometer in which the optical axis is inclined will be described. .

FIG. 12 is a configuration diagram of the shearing interferometer of the present embodiment.

The splitting optical system 64 of this shearing interferometer has a beam splitter (here, a half mirror) HM64 and a beam splitter similar to the splitting optical system 34 shown in FIG. Evening (here, half mirror) HM33, Mira M34-l, and Mirror M34-2 are arranged.

However, the postures of the mirror M34-2 and the half-mirror HM64 are adjusted so that the light beam L1 and the light beam L2 are incident on the surface 4 to be inspected with their optical axes inclined by 0. I have.

Further, in this embodiment, it is not necessary to use a polarizing beam splitter at the position of the half mirror HM64 (in the case of the shearing interferometer in FIG. 8, the polarizing beam splitter is used to separate the light beam L1 and the light beam L2). I used the evening ..). Accordingly, the polarizing plate 35 shown in FIG. 8 is unnecessary.

The light beam L1 and the light beam L2 that have entered the surface 4 to be inspected return to another optical path in the split optical system 64 while keeping the optical axis inclined, and enter the imaging optical system 7 and the CCD camera 3 in that order. .

In Shiaringu interferometer of the present embodiment, the inclination of the optical axis of the light beam 1 and the light beam L 2 at the time of entering the test surface 4 not being absorbed back and forth division optical system 64 _c, however, is on the imaging surface The noise wavefront superimposed on the wavefront of the light beam L1 and the noise wavefront superimposed on the wavefront of the light beam L2 just overlap, and the reflection corresponding to the unevenness of the surface 4 to be measured, which is superimposed on the light beam L1 The wavefront (signal wavefront) and the signal wavefront superimposed on the light beam L2 deviate from each other.

Therefore, the interference fringes formed by the light flux L1 and the light flux L2 on the imaging surface are affected by the reflected wavefront (signal wavefront) corresponding to the unevenness of the test surface 4 but not by the noise wavefront. .

Further, in this shearing interferometer, it is desirable that a mask M61 be disposed on the focal plane of the imaging optical system 7.

The mask M61 is provided with two openings, and the distance d between the two openings is set to d = 2f0 (where is the focal length of the imaging optical system 7).

The direction in which the two openings are arranged is set so as to correspond to the above-described inclination direction of the optical axis. In this way, the light beams L 1 and L 2 individually transmit one of the two openings and the other, and form interference fringes on the imaging surface of the CCD camera 3.

Therefore, interference fringes caused by the light beams L1 and L2 are detected with high accuracy without being affected by other light.

[Supplement to each embodiment]

In each of the above embodiments, in order to accurately evaluate the projection optical system PL or the test surface 4, it is necessary to detect interference fringes at least once after changing the direction of wavefront division.

Incidentally, in order to change the direction of division in the first embodiment or the second embodiment, the division optical element (diffractive optical element) and the mask (the mask having two openings) are respectively set along the optical axis. Can be rotated by an equal angle.

[Seventh embodiment]

A seventh embodiment of the present invention will be described based on FIG.

In the present embodiment, a description will be given of a projection exposure apparatus manufactured using the above embodiments.

FIG. 13 is a schematic configuration diagram of the projection exposure apparatus of the present embodiment.

The whole or a part of the projection optical system PL mounted on the projection exposure apparatus is inspected at the time of its manufacture by the interference measurement according to any of the above embodiments.

Then, at least one surface of the projection optical system PL and / or any part of the projection exposure apparatus are adjusted according to the measurement result.

According to the above embodiments, since the measurement is performed with high accuracy, the projection optical system PL and / or the projection exposure apparatus have high performance even if the adjustment method is the same as the conventional one.

The projection exposure apparatus includes a projection optical system PL, a wafer stage 108 for mounting a wafer w, a reticle stage 105 for mounting a reticle r, and a light source section 101 for supplying light to the reticle r. And so on.

A reticle r and a wafer w are arranged on the object plane and the image plane of the projection optical system PL, respectively.

The projection exposure apparatus has a stage control for controlling the position of the stage 108. Control 107 is provided.

Further, the projection optical system PL has an alignment optical system applied to a scan type projection exposure apparatus.

The illumination optical system 102 has an alignment optical system 103 for adjusting the relative position between the reticle r and the wafer w.

Further, reticle stage 105 can move reticle r in parallel with respect to surface 108 a of wafer stage 108.

Further, the projection exposure apparatus is provided with a reticle exchange system 104 for exchanging and transporting the reticle r set on the reticle stage 105.

The reticle exchange system 104 has a stage driver (not shown) for relatively moving the reticle stage 105 with respect to the surface 10.8a of the wafer stage 108.

Further, the projection exposure apparatus is also provided with a main control unit 109 which performs control relating to a series of processes “from alignment to exposure”.

As described above, according to the present invention, a shearing interferometer and a shearing interferometer capable of performing measurement without being affected by disturbance or aberration on the light source side are realized.

Further, according to the present invention, a high-performance projection optical system manufacturing method, a high-performance projection optical system, and a high-performance projection exposure apparatus are realized by applying the shearing interference measurement method.

Thus, the present invention contributes to improvement of semiconductor manufacturing technology.

Claims

The scope of the claims

(1) The measurement light beam emitted from the light source is divided to generate two light beams with wavefronts shifted from each other, and the two light beams are projected on the test object with the wavefront shifted,

Detecting an interference fringe that occurs at a position where the wavefronts of the two light beams passing through the object overlap each other.

A method for measuring shearing interference.

(2) In the shearing interference measurement method according to claim 1,

Applying a phase shift interference method for detecting the interference fringes a plurality of times while shifting the phase of the two light beams

A method for measuring shearing interference.

(3) It is arranged in the optical path of the measurement light beam emitted from the light source, and splits the measurement light beam to generate two light beams whose wavefronts are shifted from each other, and the two light beams are tested with the wavefronts shifted. A split optical system that projects light onto an object,

A detector disposed at a position where the wavefronts of the two light beams transmitted through the test object overlap with each other; and

A shearing interferometer comprising:

(4) In the shearing interferometer according to claim 3,

The arrangement position of the detector,

It is a position conjugate with the division plane of the division optical system.

A shearing interferometer.

(5) In the shearing interferometer according to claim 3,

In the optical path of the two light beams that pass through the test object and enter the detector,

A splitting optical system is arranged, which divides the two light beams and superposes the wavefronts of the two light beams on the detector.

A shearing interferometer.

(6) In the shearing interferometer according to claim 5,

A splitting optical system for splitting the measurement light beam, and a splitting optical system for splitting the two light beams again Are conjugated

A shearing interferometer.

(7) In the shearing interferometer according to any one of claims 3 to 6, in the optical path of the two light beams,

A mask is arranged to focus light other than the two light beams whose wavefronts overlap on the detector.

A shearing interferometer.

(8) In the shearing interferometer according to any one of claims 3 to 7, the split optical system includes:

Consisting of a diffractive optical element

A shearing interferometer.

(9) It is placed in the optical path of the measurement light beam emitted from the light source, and splits the measurement light beam to generate two light beams whose wavefronts are shifted from each other, and the two light beams are inspected with the wavefronts shifted. A split optical system that projects light onto an object,

A detector arranged at a position where the wavefronts of the two light beams returned from the test object to the split optical system overlap each other;

A shearing interferometer comprising:

(10) In the shearing interferometer according to claim 9,

The split optical system includes:

A beam splitter that splits the measurement light beam into two light beams of a transmitted light beam and a reflected light beam; and a deflection device that projects the two light beams split by the beam splitter onto a test object in a state where their wavefronts are shifted from each other. Optical system

A shearing interferometer.

(11) In the shearing interferometer according to claim 10,

In the beam split evening,

Polarized beam splitters are used,

In the optical path of the two light beams between the split optical system and the detector,

Polarizer is arranged

A shearing interferometer.

(12) In the shearing interferometer according to claim 9 or claim 10, the arrangement position of the detector is:

It is a position conjugate with the surface to be inspected of the object.

A shearing interferometer.

(13) In the sealing interferometer according to claim 12,

In the optical path of the two light beams,

A shearing interferometer.

(14) Including a procedure for inspecting part or all of the projection optical system by the shearing interference measurement method according to claim 1 or 2.

A method of manufacturing a projection optical system.

(15) A projection optical system manufactured by the method for manufacturing a projection optical system according to claim 14.

(16) Including the projection optical system according to claim 15

A projection exposure apparatus characterized by the above-mentioned.